<!DOCTYPE HTML>
<html lang="zh-CN">


<head>
    <meta charset="utf-8">
    <meta name="keywords" content="IP协议看这篇就够了, Gtwff">
    <meta name="description" content="">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=no">
    <meta name="renderer" content="webkit|ie-stand|ie-comp">
    <meta name="mobile-web-app-capable" content="yes">
    <meta name="format-detection" content="telephone=no">
    <meta name="apple-mobile-web-app-capable" content="yes">
    <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent">
    <meta name="referrer" content="no-referrer-when-downgrade">
    <!-- Global site tag (gtag.js) - Google Analytics -->

<script async src="https://www.googletagmanager.com/gtag/js?id="></script>
<script>
    window.dataLayer = window.dataLayer || [];
    function gtag() {
        dataLayer.push(arguments);
    }

    gtag('js', new Date());
    gtag('config', '');
</script>


    <title>IP协议看这篇就够了 | Gtwff</title>
    <link rel="icon" type="image/png" href="/favicon.png">

    <link rel="stylesheet" type="text/css" href="/libs/awesome/css/all.css">
    <link rel="stylesheet" type="text/css" href="/libs/materialize/materialize.min.css">
    <link rel="stylesheet" type="text/css" href="/libs/aos/aos.css">
    <link rel="stylesheet" type="text/css" href="/libs/animate/animate.min.css">
    <link rel="stylesheet" type="text/css" href="/libs/lightGallery/css/lightgallery.min.css">
    <link rel="stylesheet" type="text/css" href="/css/matery.css">
    <link rel="stylesheet" type="text/css" href="/css/my.css">

    <script src="/libs/jquery/jquery.min.js"></script>

<meta name="generator" content="Hexo 5.4.0"></head>



   <style>
    body{
       background-image: url(https://cdn.jsdelivr.net/gh/Tokisaki-Galaxy/res/site/medias/background.jpg);
       background-repeat:no-repeat;
       background-size:cover;
       background-attachment:fixed;
    }
</style>



<body>
    <header class="navbar-fixed">
    <nav id="headNav" class="bg-color nav-transparent">
        <div id="navContainer" class="nav-wrapper container">
            <div class="brand-logo">
                <a href="/" class="waves-effect waves-light">
                    
                    <img src="/medias/logo.png" class="logo-img" alt="LOGO">
                    
                    <span class="logo-span">Gtwff</span>
                </a>
            </div>
            

<a href="#" data-target="mobile-nav" class="sidenav-trigger button-collapse"><i class="fas fa-bars"></i></a>
<ul class="right nav-menu">
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/" class="waves-effect waves-light">
      
      <i class="fas fa-home" style="zoom: 0.6;"></i>
      
      <span>首页</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/tags" class="waves-effect waves-light">
      
      <i class="fas fa-tags" style="zoom: 0.6;"></i>
      
      <span>标签</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/categories" class="waves-effect waves-light">
      
      <i class="fas fa-bookmark" style="zoom: 0.6;"></i>
      
      <span>分类</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/archives" class="waves-effect waves-light">
      
      <i class="fas fa-archive" style="zoom: 0.6;"></i>
      
      <span>归档</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/about" class="waves-effect waves-light">
      
      <i class="fas fa-user-circle" style="zoom: 0.6;"></i>
      
      <span>关于</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/contact" class="waves-effect waves-light">
      
      <i class="fas fa-comments" style="zoom: 0.6;"></i>
      
      <span>留言板</span>
    </a>
    
  </li>
  
  <li class="hide-on-med-and-down nav-item">
    
    <a href="/friends" class="waves-effect waves-light">
      
      <i class="fas fa-address-book" style="zoom: 0.6;"></i>
      
      <span>友情链接</span>
    </a>
    
  </li>
  
  <li>
    <a href="#searchModal" class="modal-trigger waves-effect waves-light">
      <i id="searchIcon" class="fas fa-search" title="搜索" style="zoom: 0.85;"></i>
    </a>
  </li>
</ul>


<div id="mobile-nav" class="side-nav sidenav">

    <div class="mobile-head bg-color">
        
        <img src="/medias/logo.png" class="logo-img circle responsive-img">
        
        <div class="logo-name">Gtwff</div>
        <div class="logo-desc">
            
            Never really desperate, only the lost of the soul.
            
        </div>
    </div>

    <ul class="menu-list mobile-menu-list">
        
        <li class="m-nav-item">
	  
		<a href="/" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-home"></i>
			
			首页
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/tags" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-tags"></i>
			
			标签
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/categories" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-bookmark"></i>
			
			分类
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/archives" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-archive"></i>
			
			归档
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/about" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-user-circle"></i>
			
			关于
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/contact" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-comments"></i>
			
			留言板
		</a>
          
        </li>
        
        <li class="m-nav-item">
	  
		<a href="/friends" class="waves-effect waves-light">
			
			    <i class="fa-fw fas fa-address-book"></i>
			
			友情链接
		</a>
          
        </li>
        
        
        <li><div class="divider"></div></li>
        <li>
            <a href="https://gitee.com/kuangty/kuangty" class="waves-effect waves-light" target="_blank">
                <i class="fab fa-github-square fa-fw"></i>Fork Me
            </a>
        </li>
        
    </ul>
</div>


        </div>

        
            <style>
    .nav-transparent .github-corner {
        display: none !important;
    }

    .github-corner {
        position: absolute;
        z-index: 10;
        top: 0;
        right: 0;
        border: 0;
        transform: scale(1.1);
    }

    .github-corner svg {
        color: #0f9d58;
        fill: #fff;
        height: 64px;
        width: 64px;
    }

    .github-corner:hover .octo-arm {
        animation: a 0.56s ease-in-out;
    }

    .github-corner .octo-arm {
        animation: none;
    }

    @keyframes a {
        0%,
        to {
            transform: rotate(0);
        }
        20%,
        60% {
            transform: rotate(-25deg);
        }
        40%,
        80% {
            transform: rotate(10deg);
        }
    }
</style>

<a href="https://gitee.com/kuangty/kuangty" class="github-corner tooltipped hide-on-med-and-down" target="_blank"
   data-tooltip="Fork Me" data-position="left" data-delay="50">
    <svg viewBox="0 0 250 250" aria-hidden="true">
        <path d="M0,0 L115,115 L130,115 L142,142 L250,250 L250,0 Z"></path>
        <path d="M128.3,109.0 C113.8,99.7 119.0,89.6 119.0,89.6 C122.0,82.7 120.5,78.6 120.5,78.6 C119.2,72.0 123.4,76.3 123.4,76.3 C127.3,80.9 125.5,87.3 125.5,87.3 C122.9,97.6 130.6,101.9 134.4,103.2"
              fill="currentColor" style="transform-origin: 130px 106px;" class="octo-arm"></path>
        <path d="M115.0,115.0 C114.9,115.1 118.7,116.5 119.8,115.4 L133.7,101.6 C136.9,99.2 139.9,98.4 142.2,98.6 C133.8,88.0 127.5,74.4 143.8,58.0 C148.5,53.4 154.0,51.2 159.7,51.0 C160.3,49.4 163.2,43.6 171.4,40.1 C171.4,40.1 176.1,42.5 178.8,56.2 C183.1,58.6 187.2,61.8 190.9,65.4 C194.5,69.0 197.7,73.2 200.1,77.6 C213.8,80.2 216.3,84.9 216.3,84.9 C212.7,93.1 206.9,96.0 205.4,96.6 C205.1,102.4 203.0,107.8 198.3,112.5 C181.9,128.9 168.3,122.5 157.7,114.1 C157.9,116.9 156.7,120.9 152.7,124.9 L141.0,136.5 C139.8,137.7 141.6,141.9 141.8,141.8 Z"
              fill="currentColor" class="octo-body"></path>
    </svg>
</a>
        
    </nav>

</header>

    



<div class="bg-cover pd-header post-cover" style="background-image: url('/medias/featureimages/13.jpg')">
    <div class="container" style="right: 0px;left: 0px;">
        <div class="row">
            <div class="col s12 m12 l12">
                <div class="brand">
                    <h1 class="description center-align post-title">IP协议看这篇就够了</h1>
                </div>
            </div>
        </div>
    </div>
</div>




<main class="post-container content">

    
    <link rel="stylesheet" href="/libs/tocbot/tocbot.css">
<style>
    #articleContent h1::before,
    #articleContent h2::before,
    #articleContent h3::before,
    #articleContent h4::before,
    #articleContent h5::before,
    #articleContent h6::before {
        display: block;
        content: " ";
        height: 100px;
        margin-top: -100px;
        visibility: hidden;
    }

    #articleContent :focus {
        outline: none;
    }

    .toc-fixed {
        position: fixed;
        top: 64px;
    }

    .toc-widget {
        width: 345px;
        padding-left: 20px;
    }

    .toc-widget .toc-title {
        padding: 35px 0 15px 17px;
        font-size: 1.5rem;
        font-weight: bold;
        line-height: 1.5rem;
    }

    .toc-widget ol {
        padding: 0;
        list-style: none;
    }

    #toc-content {
        padding-bottom: 30px;
        overflow: auto;
    }

    #toc-content ol {
        padding-left: 10px;
    }

    #toc-content ol li {
        padding-left: 10px;
    }

    #toc-content .toc-link:hover {
        color: #42b983;
        font-weight: 700;
        text-decoration: underline;
    }

    #toc-content .toc-link::before {
        background-color: transparent;
        max-height: 25px;

        position: absolute;
        right: 23.5vw;
        display: block;
    }

    #toc-content .is-active-link {
        color: #42b983;
    }

    #floating-toc-btn {
        position: fixed;
        right: 15px;
        bottom: 76px;
        padding-top: 15px;
        margin-bottom: 0;
        z-index: 998;
    }

    #floating-toc-btn .btn-floating {
        width: 48px;
        height: 48px;
    }

    #floating-toc-btn .btn-floating i {
        line-height: 48px;
        font-size: 1.4rem;
    }
</style>
<div class="row">
    <div id="main-content" class="col s12 m12 l9">
        <!-- 文章内容详情 -->
<div id="artDetail">
    <div class="card">
        <div class="card-content article-info">
            <div class="row tag-cate">
                <div class="col s7">
                    
                    <div class="article-tag">
                        
                            <a href="/tags/IP-%E5%8D%8F%E8%AE%AE/">
                                <span class="chip bg-color">IP 协议</span>
                            </a>
                        
                    </div>
                    
                </div>
                <div class="col s5 right-align">
                    
                    <div class="post-cate">
                        <i class="fas fa-bookmark fa-fw icon-category"></i>
                        
                            <a href="/categories/%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C/" class="post-category">
                                计算机网络
                            </a>
                        
                    </div>
                    
                </div>
            </div>

            <div class="post-info">
                
                <div class="post-date info-break-policy">
                    <i class="far fa-calendar-minus fa-fw"></i>发布日期:&nbsp;&nbsp;
                    2021-10-23
                </div>
                

                
                <div class="post-date info-break-policy">
                    <i class="far fa-calendar-check fa-fw"></i>更新日期:&nbsp;&nbsp;
                    2022-03-27
                </div>
                

                
                <div class="info-break-policy">
                    <i class="far fa-file-word fa-fw"></i>文章字数:&nbsp;&nbsp;
                    3.4k
                </div>
                

                
                <div class="info-break-policy">
                    <i class="far fa-clock fa-fw"></i>阅读时长:&nbsp;&nbsp;
                    12 分
                </div>
                

                
                    <div id="busuanzi_container_page_pv" class="info-break-policy">
                        <i class="far fa-eye fa-fw"></i>阅读次数:&nbsp;&nbsp;
                        <span id="busuanzi_value_page_pv"></span>
                    </div>
				
            </div>
        </div>
        <hr class="clearfix">

        
        <!-- 是否加载使用自带的 prismjs. -->
        <link rel="stylesheet" href="/libs/prism/prism.css">
        

        
        <!-- 代码块折行 -->
        <style type="text/css">
            code[class*="language-"], pre[class*="language-"] { white-space: pre-wrap !important; }
        </style>
        

        <div class="card-content article-card-content">
            <div id="articleContent">
                <h2 id="IP-协议的基本认知"><a href="#IP-协议的基本认知" class="headerlink" title="IP 协议的基本认知"></a>IP 协议的基本认知</h2><p>IP（Internet Protocol）协议，中文叫网际协议 ，是位于网络层的一个协议。它用于屏蔽下层物理网络的差异，为上层提供统一的 IP 数据报。就像下面这样：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/IP1.png" alt="IP1" style="zoom:80%;" />

<p>IP 协议的特点：IP 协议提供无连接的、不可靠的、尽力的数据报投递服务：</p>
<ul>
<li>无连接的投递服务：发送端可于任何时候自由发送数据，而接收端永远不知道自己会在何时从哪里接收到数据。每个 IP 数据报独立处理和传输， 一台主机发出的数据报序列，可能会走不同的路径， 甚至有可能其中的一部分数据报会在传输过程中丢失。</li>
<li>不可靠的投递服务：IP 协议本身不保证 IP 数据报投递的结果，在传输的过程中，IP 数据报可能会丢失、重复、延迟和乱序等， IP 协议不对内容作任何检测，也不将这些结果通知收发双方。</li>
<li>尽力投递服务：每个数据链路上会规定一个最大传输单元 MTU，如果 IP 数据报的长度超过 MTU，那么网络层就会把这些报文分割成一个一个的小组（分组）进行传送，以适应具体的传输网络。</li>
</ul>
<h2 id="IP-地址"><a href="#IP-地址" class="headerlink" title="IP 地址"></a>IP 地址</h2><h3 id="IP-地址的基本认知"><a href="#IP-地址的基本认知" class="headerlink" title="IP 地址的基本认知"></a>IP 地址的基本认知</h3><p>IP 地址（IPv4 地址）由 <code>32</code> 位正整数来表示，IP 地址在计算机是以二进制的方式处理的。而人类为了方便记忆采用了<strong>点分十进制</strong>的标记方式，也就是将 32 位 IP 地址以每 8 位为组，共分为 <code>4</code> 组，每组以「<code>.</code>」隔开，再将每组转换成十进制。</p>
<p>IP 地址的作用：在 TCP/IP 网络通信时，为了保证能正常通信，每个设备都需要配置正确的 IP 地址，否则无法实现正常的通信，IP 地址是全世界唯一的。</p>
<p>我们知道了IP地址有32位，那么 IP 地址的最大值就是 2^32 ，大约是43亿。那么意味着理论上最大允许 43 亿台计算机连接到网络。但是实际却不是这样，IP 地址并不是根据主机台数来配置的，而是以网卡。像服务器、路由器等设备都是有 2 个以上的网卡，也就是它们会有 2 个以上的 IP 地址。</p>
<h3 id="IP-地址与-MAC-地址"><a href="#IP-地址与-MAC-地址" class="headerlink" title="IP 地址与 MAC 地址"></a>IP 地址与 MAC 地址</h3><p>这里简单的说一下 IP 地址与 MAC 地址的关系（什么，你不知道 MAC 地址，等我🙃🙃🙃）。那既然有了 MAC 地址，为啥还要 IP 地址呢？</p>
<p>MAC 的作用则是实现直连的两个设备之间通信，而 IP 则负责在没有直连的两个网络之间进行通信传输。怎么理解这句话呢？</p>
<p>我们知道 IP 是网络层的，网络层指定了从哪个主机（源 IP 地址）发送到哪个主机（目的 IP 地址），源 IP 地址和目标 IP 地址在传输过程中是不会变化的。而数据链路层则是根据 MAC 地址在一个接一个的区间中进行传输的，每个区间内的出发地址即源 MAC 地址，每个区间内的目的地址即目的 MAC 地址。显然，随着数据的传输，源 MAC 地址和目的 MAC 地址会不断的发生变化。就像下图这样：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119104050308.png" alt="image-20211119104050308" style="zoom:80%;" />

<h3 id="IP-地址的分类"><a href="#IP-地址的分类" class="headerlink" title="IP 地址的分类"></a>IP 地址的分类</h3><p>IP 地址分类成了 5 种类型，分别是 A 类、B 类、C 类、D 类、E 类，如下图所示：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119105027526.png" alt="image-20211119105027526" style="zoom:80%;" />

<p>从图中可以看出：橙色的叫做分类号，用以区分 IP 地址类别。其中对于 A、B、C 类主要分为两个部分，分别是网络号和主机号。那什么是网络号和主机号呢？</p>
<ul>
<li>网络号表示其属于互联网的哪一个网络。</li>
<li>主机号表示其属于该网络中的哪一台主机。</li>
</ul>
<p>那这两个是用来干什么的呢？</p>
<p>因为两台计算机要通讯，首先要判断是否处于同一个广播域内，即网络地址（网络号）是否相同：</p>
<ul>
<li>如果网络地址相同，表明接受方在本网络上（本地网络主机），那么可以把数据包直接发送到目标主机，无需转发给其他的网络。</li>
<li>网络号不相同的主机称之为远程网络主机，远程网络中的主机要相互通信必须通过本地网关来传递转发数据。</li>
</ul>
<p>路由器寻址工作中，也就是通过这样的方式来找到对应的网络号的，进而把数据包转发给对应的网络内。就像下图这样：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119111251428.png" alt="image-20211119111251428" style="zoom:80%;" />

<p>那这样的分类方式有啥优点呢？</p>
<p>不管是路由器还是主机解析到一个 IP 地址时候，我们判断其 IP 地址的首位是否为 0，为 0 则为 A 类地址，那么就能很快的找出网络地址和主机地址，就像下图这样：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119112049255.png" alt="image-20211119112049255" style="zoom:80%;" />

<p>那 A、B、C 分类对应的地址范围，最大主机数如下表所示：</p>
<table>
<thead>
<tr>
<th>类别</th>
<th>IP 地址范围</th>
<th>最大主机数</th>
</tr>
</thead>
<tbody><tr>
<td>A</td>
<td>0.0.0.0 ~ 127.255.255.255</td>
<td>16777214</td>
</tr>
<tr>
<td>B</td>
<td>128.0.0.0 ~ 191.255.255.255</td>
<td>65534</td>
</tr>
<tr>
<td>C</td>
<td>192.0.0.0 ~ 233.255.255.255</td>
<td>254</td>
</tr>
</tbody></table>
<p>但是上面的地址并不是都可用，我们看下表：</p>
<table>
<thead>
<tr>
<th>类别</th>
<th>第一个可用网络号</th>
<th>最后一个可用网络号</th>
</tr>
</thead>
<tbody><tr>
<td>A</td>
<td>1</td>
<td>126</td>
</tr>
<tr>
<td>B</td>
<td>128.1</td>
<td>191.255</td>
</tr>
<tr>
<td>C</td>
<td>192.0.1</td>
<td>223.255.255</td>
</tr>
</tbody></table>
<p>下面我们看看第一个可用的网络号如何计算出来的？以 B 类地址为例：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119193205837.png" alt="image-20211119193205837" style="zoom:80%;" />

<p>那为啥是128.1而不是128.0呢？因为网络号全 0  代表此网络，因此可用的网络号应该是从1开始。就像下图这样：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119193801414.png" alt="image-20211119193801414" style="zoom:80%;" />

<p>那最后一个可用网络号是怎么计算出来的呢？很简单，就是网络号全是 1 即可，如下图：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119193933690.png" alt="image-20211119193933690" style="zoom:80%;" />

<p>为什么网络中的最大主机数为什么都要减 2  呢？</p>
<p>首先我们要明白，计算网络中的最大主机数就是要看主机号的位数，比如 B 类地址的主机号占 16 位，那么 B 类地址的最大主机个数就是 2^16 - 2 个。为什么要减 2 呢？</p>
<p>那是因为主机号全为 0 和主机号全为 1 的这两个 IP 地址是特殊的，主机号全为 1 指定某个网络下的所有主机，用于广播；主机号全为 0 指定某个网络。</p>
<h3 id="IP-单播-广播-多播"><a href="#IP-单播-广播-多播" class="headerlink" title="IP 单播/广播/多播"></a>IP 单播/广播/多播</h3><p><strong>广播</strong></p>
<p>上面我们提到了主机号全为 1 指定某个网络下的所有主机，用于广播，那么什么是广播呢？</p>
<p>广播地址用于在同一个链路中相互连接的主机之间发送数据包，即一个发送方对应多个接收方。接收方在接收到数据包之后，可以根据自己的需要选择接收还是丢弃。</p>
<p>广播地址可以分为本地广播和直接广播两种：</p>
<p>1）在本网络内广播的叫做本地广播。例如网络地址为 <code>192.168.0.0/24</code> （这种 IP 表示我们下文会讲解）的情况下，广播地址是 <code>192.168.0.255</code>。因为这个广播地址的 IP 包会被路由器屏蔽（即路由器不转发该广播包，广播包无法穿透路由器），所以不会到达 <code>192.168.0.0/24</code> 以外的其他链路上。如下图：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119201510421.png" alt="image-20211119201510421" style="zoom:80%;" />

<p>2）在不同网络之间的广播叫做直接广播。例如网络地址为 <code>192.168.0.0/24</code> 的主机向 <code>192.168.1.255/24</code> 的目标地址发送 IP 包。收到这个包的路由器，将数据转发给 <code>192.168.1.0/24</code>，从而使得所有 <code>192.168.1.1</code> ~ <code>192.168.1.254</code> 的主机都能收到这个包。如下图所示：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119201800897.png" alt="image-20211119201800897" style="zoom:80%;" />

<p><strong>单播</strong></p>
<p>广播模式下，有一个发送方，多个接收方，而在单播模式下，只有一个发送方和一个接收方。单播是可以穿透路由器的，也即路由器会对数据包其进行转发：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119202159520.png" alt="image-20211119202159520" style="zoom:80%;" />

<p><strong>多播</strong></p>
<p>上面我们讲了 A、B、C 类地址，D、E 类还没讲。D 类和 E 类地址是没有主机号的，所以不可用于主机 IP。多播使用 D 类地址，因此如果首位是 1110，就可以认为是多播地址，而剩下的 28 位可以称为多播的组编号。E 类是预留的分类，暂时未使用。</p>
<p>那么什么是多播（组播）呢？多播用于将包发送给特定组内的所有主机（可以穿透路由器），即一个发送方，特定的多个接收方。由于其直接使用 IP 协议，因此也不存在可靠传输。</p>
<p> 在人们使用多播功能之前，一直采用广播的方式。通过广播将数据发送给所有终端主机，再由这些主机 IP 之上的一层去判断是否有必要接收数据。这种方式会给那些毫无关系的网络或主机带来影响，造成网络上很多不必要的流量。再者，由于我们在大部分情况下使用的本地广播是无法穿透路由的，所以多播这种既能够穿透路由，又可以实现只给那些必要的组发送数据包的技术就成为必选之路了。如下图所示：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119202933189.png" alt="image-20211119202933189" style="zoom:80%;" />

<h3 id="子网划分"><a href="#子网划分" class="headerlink" title="子网划分"></a>子网划分</h3><p><strong>为什么要进行子网划分</strong></p>
<p>网络号相同的计算机属于同一个网络，以 B 类网络为例，网络号 16 位（除分类号 “10”，还有14 位），也就是说理论上一个链路上允许大约 2^16 ≈ 6 万台计算机连接。然而，在实际架构中，一般不会出现一个链路上连接这么多计算机的情况。因此，直接使用 A 类、B 类或 C 类地址，确实有些浪费资源，因此出现了子网划分来减少这种浪费。</p>
<p><strong>子网划分</strong></p>
<p>所谓子网划分就是：将传统的两级 IP 地址（网络号 + 主机号）转换成粒度更小的三级 IP 地址（网络号 + 子网号 + 主机号），也就是将主机地址划分为子网号和子网内的主机号。</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119211615456.png" alt="image-20211119211615456" style="zoom:80%;" />

<p>同样的，子网主机号不能全 0 或全 1。</p>
<p>注意：某单位划分子网后，对外仍表现为一个网络，即本单位外的网络看不见本单位内的子网划分。如下图所示，将网络地址 <code>145.13.0.0</code> （B类地址）划分成 3 个子网，子网的网络地址分别为 <code>145.13.3.0</code>、<code>145.13.7.0</code>、<code>145.13.21.0</code>：</p>
<blockquote>
<p>所谓网络地址就是只指定了网络号，未指定主机号，主机号全 0。</p>
<p>子网的网络地址就是指定了网络号和子网号，未指定主机号，主机号全 0。</p>
</blockquote>
<p>如下图所示：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119213154254.png" alt="image-20211119213154254" style="zoom:80%;" />

<p><strong>子网掩码</strong></p>
<p>那么，子网具体是怎么划分的呢？</p>
<p>这里就需要引出一个新的概念：子网掩码 subnet mask。子网掩码只有一个作用，就是将某个 IP 地址划分成网络地址和主机地址两部分</p>
<p>子网掩码由一连串的 0 和 1 构成（0 或 1 必须连续），二级 IP 地址中的网络号和三级 IP 地址中的网络号 + 子网号对应到子网掩码中都用 1 来表示，而主机号对应到子网掩码中用 0 来表示。因此 A、B、C 类的子网掩码如下：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119214743397.png" alt="image-20211119214743397" style="zoom:80%;" />

<p>将 IP 地址与子网掩码做按位 AND（与）运算（只有两个都为 1，结果才为 1，否则为 0），得出的就是网络地址。</p>
<h3 id="IPV4-地址"><a href="#IPV4-地址" class="headerlink" title="IPV4 地址"></a>IPV4 地址</h3><p>随着全球上网用户量越来越大，现行的 IPV4 地址越来越不够用，拯救枯竭的 IPV4 地址势在必行：</p>
<ul>
<li>方案一：无分类 IP 地址 CIDR</li>
<li>方案二：NAT 地址转换</li>
<li>……..</li>
</ul>
<p>然而，这些方案仅仅是解决燃煤之急，相对缓解了 IPV4 地址不够用的问题，但是 IPV4 地址的数量本身有限的事实无法改变，最根本的解决办法还是使用 128 比特的 IPV6 地址。</p>
<p><strong>无分类 IP 地址 CIDR</strong></p>
<p>CIDR 就是采用任意长度分割 IP 地址的网络号和主机号，像<code>a.b.c.d/x</code>，其中 <code>/x</code> 表示前 x 位属于网络号， x 的范围是 <code>0 ~ 32</code>，这就使得 IP 地址更加具有灵活性。</p>
<p>比如 10.100.122.2/24，这种地址表示形式就是 CIDR，<code>/24</code> 表示前 24 位是网络号，剩余的 8 位是主机号。</p>
<p>CIDR 把网络号都相同的连续 IP 地址组成一个 CIDR 地址块。这样，我们就可以把原来的多个 IP 地址合并成同一个网络，更有效的利用 IPV4 地址。举个例子，应用 CIDR 技术将 <code>203.183.224.1</code> 到 <code>203.183.225.254</code> 的地址合并为同一个网络（它们本来是 2 个 C 类地址）：</p>
<img src="https://cdn.jsdelivr.net/gh/kuangtianyu/img/img/image-20211119222616789.png" alt="image-20211119222616789" style="zoom:80%;" />

<p>上例中，合并该区间的地址后，主机数为 2^9 - 2 = 510 个，也就是说从 <code>203.183.224.1</code> 到 <code>203.183.225.254</code> 的这个网络内允许接入 510 台主机。</p>
<blockquote>
<p>引用地址：</p>
<p><a target="_blank" rel="noopener" href="https://mp.weixin.qq.com/s?__biz=MzUxODAzNDg4NQ==&amp;mid=2247484043&amp;idx=1&amp;sn=8e71338b2e62e7a6a7caaa7eb12defab&amp;chksm=f98e4621cef9cf37ec18e1778dfac0c9bf46d056236c8df346f4e14af20f00f39c7019166512&amp;scene=178&amp;cur_album_id=1337204681134751744#rd">https://mp.weixin.qq.com/s?__biz=MzUxODAzNDg4NQ==&amp;mid=2247484043&amp;idx=1&amp;sn=8e71338b2e62e7a6a7caaa7eb12defab&amp;chksm=f98e4621cef9cf37ec18e1778dfac0c9bf46d056236c8df346f4e14af20f00f39c7019166512&amp;scene=178&amp;cur_album_id=1337204681134751744#rd</a></p>
<p><a target="_blank" rel="noopener" href="https://mp.weixin.qq.com/s?__biz=MzI0NDc3ODE5OQ==&amp;mid=2247484306&amp;idx=1&amp;sn=0498760c107b773d01a79c340c7f3fcd&amp;scene=19#wechat_redirect">https://mp.weixin.qq.com/s?__biz=MzI0NDc3ODE5OQ==&amp;mid=2247484306&amp;idx=1&amp;sn=0498760c107b773d01a79c340c7f3fcd&amp;scene=19#wechat_redirect</a></p>
</blockquote>

                
            </div>
            <hr/>

            

    <div class="reprint" id="reprint-statement">
        
            <div class="reprint__author">
                <span class="reprint-meta" style="font-weight: bold;">
                    <i class="fas fa-user">
                        文章作者:
                    </i>
                </span>
                <span class="reprint-info">
                    <a href="/about" rel="external nofollow noreferrer">Gtwff</a>
                </span>
            </div>
            <div class="reprint__type">
                <span class="reprint-meta" style="font-weight: bold;">
                    <i class="fas fa-link">
                        文章链接:
                    </i>
                </span>
                <span class="reprint-info">
                    <a href="https://kuangty.gitee.io/2021/10/23/%E8%AE%A1%E7%BD%91/IP/">https://kuangty.gitee.io/2021/10/23/%E8%AE%A1%E7%BD%91/IP/</a>
                </span>
            </div>
            <div class="reprint__notice">
                <span class="reprint-meta" style="font-weight: bold;">
                    <i class="fas fa-copyright">
                        版权声明:
                    </i>
                </span>
                <span class="reprint-info">
                    本博客所有文章除特別声明外，均采用
                    <a href="https://creativecommons.org/licenses/by/4.0/deed.zh" rel="external nofollow noreferrer" target="_blank">CC BY 4.0</a>
                    许可协议。转载请注明来源
                    <a href="/about" target="_blank">Gtwff</a>
                    !
                </span>
            </div>
        
    </div>

    <script async defer>
      document.addEventListener("copy", function (e) {
        let toastHTML = '<span>复制成功，请遵循本文的转载规则</span><button class="btn-flat toast-action" onclick="navToReprintStatement()" style="font-size: smaller">查看</a>';
        M.toast({html: toastHTML})
      });

      function navToReprintStatement() {
        $("html, body").animate({scrollTop: $("#reprint-statement").offset().top - 80}, 800);
      }
    </script>



            <div class="tag_share" style="display: block;">
                <div class="post-meta__tag-list" style="display: inline-block;">
                    
                        <div class="article-tag">
                            
                                <a href="/tags/IP-%E5%8D%8F%E8%AE%AE/">
                                    <span class="chip bg-color">IP 协议</span>
                                </a>
                            
                        </div>
                    
                </div>
                <div class="post_share" style="zoom: 80%; width: fit-content; display: inline-block; float: right; margin: -0.15rem 0;">
                    <link rel="stylesheet" type="text/css" href="/libs/share/css/share.min.css">
<div id="article-share">

    
    <div class="social-share" data-sites="twitter,facebook,google,qq,qzone,wechat,weibo,douban,linkedin" data-wechat-qrcode-helper="<p>微信扫一扫即可分享！</p>"></div>
    <script src="/libs/share/js/social-share.min.js"></script>
    

    

</div>

                </div>
            </div>
            
                <style>
    #reward {
        margin: 40px 0;
        text-align: center;
    }

    #reward .reward-link {
        font-size: 1.4rem;
        line-height: 38px;
    }

    #reward .btn-floating:hover {
        box-shadow: 0 6px 12px rgba(0, 0, 0, 0.2), 0 5px 15px rgba(0, 0, 0, 0.2);
    }

    #rewardModal {
        width: 320px;
        height: 350px;
    }

    #rewardModal .reward-title {
        margin: 15px auto;
        padding-bottom: 5px;
    }

    #rewardModal .modal-content {
        padding: 10px;
    }

    #rewardModal .close {
        position: absolute;
        right: 15px;
        top: 15px;
        color: rgba(0, 0, 0, 0.5);
        font-size: 1.3rem;
        line-height: 20px;
        cursor: pointer;
    }

    #rewardModal .close:hover {
        color: #ef5350;
        transform: scale(1.3);
        -moz-transform:scale(1.3);
        -webkit-transform:scale(1.3);
        -o-transform:scale(1.3);
    }

    #rewardModal .reward-tabs {
        margin: 0 auto;
        width: 210px;
    }

    .reward-tabs .tabs {
        height: 38px;
        margin: 10px auto;
        padding-left: 0;
    }

    .reward-content ul {
        padding-left: 0 !important;
    }

    .reward-tabs .tabs .tab {
        height: 38px;
        line-height: 38px;
    }

    .reward-tabs .tab a {
        color: #fff;
        background-color: #ccc;
    }

    .reward-tabs .tab a:hover {
        background-color: #ccc;
        color: #fff;
    }

    .reward-tabs .wechat-tab .active {
        color: #fff !important;
        background-color: #22AB38 !important;
    }

    .reward-tabs .alipay-tab .active {
        color: #fff !important;
        background-color: #019FE8 !important;
    }

    .reward-tabs .reward-img {
        width: 210px;
        height: 210px;
    }
</style>

<div id="reward">
    <a href="#rewardModal" class="reward-link modal-trigger btn-floating btn-medium waves-effect waves-light red">赏</a>

    <!-- Modal Structure -->
    <div id="rewardModal" class="modal">
        <div class="modal-content">
            <a class="close modal-close"><i class="fas fa-times"></i></a>
            <h4 class="reward-title">你的赏识是我前进的动力</h4>
            <div class="reward-content">
                <div class="reward-tabs">
                    <ul class="tabs row">
                        <li class="tab col s6 alipay-tab waves-effect waves-light"><a href="#alipay">支付宝</a></li>
                        <li class="tab col s6 wechat-tab waves-effect waves-light"><a href="#wechat">微 信</a></li>
                    </ul>
                    <div id="alipay">
                        <img src="/medias/reward/alipay.jpg" class="reward-img" alt="支付宝打赏二维码">
                    </div>
                    <div id="wechat">
                        <img src="/medias/reward/wechat.png" class="reward-img" alt="微信打赏二维码">
                    </div>
                </div>
            </div>
        </div>
    </div>
</div>

<script>
    $(function () {
        $('.tabs').tabs();
    });
</script>

            
        </div>
    </div>

    

    

    

    

    

    

    

    

    

<article id="prenext-posts" class="prev-next articles">
    <div class="row article-row">
        
        <div class="article col s12 m6" data-aos="fade-up">
            <div class="article-badge left-badge text-color">
                <i class="fas fa-chevron-left"></i>&nbsp;上一篇</div>
            <div class="card">
                <a href="/2021/10/23/%E8%AE%A1%E7%BD%91/TCP%E5%8F%AF%E9%9D%A0%E4%BC%A0%E8%BE%93/">
                    <div class="card-image">
                        
                        
                        <img src="/medias/featureimages/13.jpg" class="responsive-img" alt="TCP 可靠传输">
                        
                        <span class="card-title">TCP 可靠传输</span>
                    </div>
                </a>
                <div class="card-content article-content">
                    <div class="summary block-with-text">
                        
                            
                        
                    </div>
                    <div class="publish-info">
                        <span class="publish-date">
                            <i class="far fa-clock fa-fw icon-date"></i>2021-10-23
                        </span>
                        <span class="publish-author">
                            
                            <i class="fas fa-bookmark fa-fw icon-category"></i>
                            
                            <a href="/categories/%E8%AE%A1%E7%AE%97%E6%9C%BA%E7%BD%91%E7%BB%9C/" class="post-category">
                                    计算机网络
                                </a>
                            
                            
                        </span>
                    </div>
                </div>
                
                <div class="card-action article-tags">
                    
                    <a href="/tags/TCP-%E5%8D%8F%E8%AE%AE/">
                        <span class="chip bg-color">TCP 协议</span>
                    </a>
                    
                </div>
                
            </div>
        </div>
        
        
        <div class="article col s12 m6" data-aos="fade-up">
            <div class="article-badge right-badge text-color">
                下一篇&nbsp;<i class="fas fa-chevron-right"></i>
            </div>
            <div class="card">
                <a href="/2021/10/08/MySQL/%E5%90%8A%E6%89%93%E9%9D%A2%E8%AF%95%E5%AE%98%E4%B9%8B-MySQL-%E4%B8%AD%E4%B8%80%E6%9D%A1-SQL-%E8%AF%AD%E5%8F%A5%E7%9A%84%E6%89%A7%E8%A1%8C%E8%BF%87%E7%A8%8B/">
                    <div class="card-image">
                        
                        
                        <img src="/medias/featureimages/22.jpg" class="responsive-img" alt="吊打面试官之 MySQL 中一条 SQL 语句的执行过程">
                        
                        <span class="card-title">吊打面试官之 MySQL 中一条 SQL 语句的执行过程</span>
                    </div>
                </a>
                <div class="card-content article-content">
                    <div class="summary block-with-text">
                        
                            
                        
                    </div>
                    <div class="publish-info">
                            <span class="publish-date">
                                <i class="far fa-clock fa-fw icon-date"></i>2021-10-08
                            </span>
                        <span class="publish-author">
                            
                            <i class="fas fa-bookmark fa-fw icon-category"></i>
                            
                            <a href="/categories/MySQL/" class="post-category">
                                    MySQL
                                </a>
                            
                            
                        </span>
                    </div>
                </div>
                
                <div class="card-action article-tags">
                    
                    <a href="/tags/MySQL-SQL%E6%89%A7%E8%A1%8C/">
                        <span class="chip bg-color">MySQL SQL执行</span>
                    </a>
                    
                </div>
                
            </div>
        </div>
        
    </div>
</article>

</div>



<!-- 代码块功能依赖 -->
<script type="text/javascript" src="/libs/codeBlock/codeBlockFuction.js"></script>

<!-- 代码语言 -->

<script type="text/javascript" src="/libs/codeBlock/codeLang.js"></script>


<!-- 代码块复制 -->

<script type="text/javascript" src="/libs/codeBlock/codeCopy.js"></script>


<!-- 代码块收缩 -->

<script type="text/javascript" src="/libs/codeBlock/codeShrink.js"></script>


    </div>
    <div id="toc-aside" class="expanded col l3 hide-on-med-and-down">
        <div class="toc-widget card" style="background-color: white;">
            <div class="toc-title"><i class="far fa-list-alt"></i>&nbsp;&nbsp;目录</div>
            <div id="toc-content"></div>
        </div>
    </div>
</div>

<!-- TOC 悬浮按钮. -->

<div id="floating-toc-btn" class="hide-on-med-and-down">
    <a class="btn-floating btn-large bg-color">
        <i class="fas fa-list-ul"></i>
    </a>
</div>


<script src="/libs/tocbot/tocbot.min.js"></script>
<script>
    $(function () {
        tocbot.init({
            tocSelector: '#toc-content',
            contentSelector: '#articleContent',
            headingsOffset: -($(window).height() * 0.4 - 45),
            collapseDepth: Number('0'),
            headingSelector: 'h1, h2, h3, h4'
        });

        // modify the toc link href to support Chinese.
        let i = 0;
        let tocHeading = 'toc-heading-';
        $('#toc-content a').each(function () {
            $(this).attr('href', '#' + tocHeading + (++i));
        });

        // modify the heading title id to support Chinese.
        i = 0;
        $('#articleContent').children('h1, h2, h3, h4').each(function () {
            $(this).attr('id', tocHeading + (++i));
        });

        // Set scroll toc fixed.
        let tocHeight = parseInt($(window).height() * 0.4 - 64);
        let $tocWidget = $('.toc-widget');
        $(window).scroll(function () {
            let scroll = $(window).scrollTop();
            /* add post toc fixed. */
            if (scroll > tocHeight) {
                $tocWidget.addClass('toc-fixed');
            } else {
                $tocWidget.removeClass('toc-fixed');
            }
        });

        
        /* 修复文章卡片 div 的宽度. */
        let fixPostCardWidth = function (srcId, targetId) {
            let srcDiv = $('#' + srcId);
            if (srcDiv.length === 0) {
                return;
            }

            let w = srcDiv.width();
            if (w >= 450) {
                w = w + 21;
            } else if (w >= 350 && w < 450) {
                w = w + 18;
            } else if (w >= 300 && w < 350) {
                w = w + 16;
            } else {
                w = w + 14;
            }
            $('#' + targetId).width(w);
        };

        // 切换TOC目录展开收缩的相关操作.
        const expandedClass = 'expanded';
        let $tocAside = $('#toc-aside');
        let $mainContent = $('#main-content');
        $('#floating-toc-btn .btn-floating').click(function () {
            if ($tocAside.hasClass(expandedClass)) {
                $tocAside.removeClass(expandedClass).hide();
                $mainContent.removeClass('l9');
            } else {
                $tocAside.addClass(expandedClass).show();
                $mainContent.addClass('l9');
            }
            fixPostCardWidth('artDetail', 'prenext-posts');
        });
        
    });
</script>

    

</main>




    <footer class="page-footer bg-color">
    
        <link rel="stylesheet" href="/libs/aplayer/APlayer.min.css">
<style>
    .aplayer .aplayer-lrc p {
        
        display: none;
        
        font-size: 12px;
        font-weight: 700;
        line-height: 16px !important;
    }

    .aplayer .aplayer-lrc p.aplayer-lrc-current {
        
        display: none;
        
        font-size: 15px;
        color: #42b983;
    }

    
    .aplayer.aplayer-fixed.aplayer-narrow .aplayer-body {
        left: -66px !important;
    }

    .aplayer.aplayer-fixed.aplayer-narrow .aplayer-body:hover {
        left: 0px !important;
    }

    
</style>
<div class="">
    
    <div class="row">
        <meting-js class="col l8 offset-l2 m10 offset-m1 s12"
                   server="netease"
                   type="playlist"
                   id="503838841"
                   fixed='true'
                   autoplay='false'
                   theme='#42b983'
                   loop='all'
                   order='random'
                   preload='auto'
                   volume='0.7'
                   list-folded='true'
        >
        </meting-js>
    </div>
</div>

<script src="/libs/aplayer/APlayer.min.js"></script>
<script src="https://cdn.jsdelivr.net/npm/meting@2/dist/Meting.min.js"></script>

    

    <div class="container row center-align"
         style="margin-bottom: 15px !important;">
        <div class="col s12 m8 l8 copy-right">
            Copyright&nbsp;&copy;
            
                <span id="year">2019-2022</span>
            
            <span id="year">2019</span>
            <a href="/about" target="_blank">Gtwff</a>
            |&nbsp;Powered by&nbsp;<a href="https://hexo.io/" target="_blank">Hexo</a>
            |&nbsp;Theme&nbsp;<a href="https://github.com/blinkfox/hexo-theme-matery" target="_blank">Matery</a>
            <br>
            
                &nbsp;<i class="fas fa-chart-area"></i>&nbsp;站点总字数:&nbsp;<span
                        class="white-color">577.4k</span>
            
            
            
                
            
            
                <span id="busuanzi_container_site_pv">
                &nbsp;|&nbsp;<i class="far fa-eye"></i>&nbsp;总访问量:&nbsp;
                    <span id="busuanzi_value_site_pv" class="white-color"></span>
            </span>
            
            
                <span id="busuanzi_container_site_uv">
                &nbsp;|&nbsp;<i class="fas fa-users"></i>&nbsp;总访问人数:&nbsp;
                    <span id="busuanzi_value_site_uv" class="white-color"></span>
            </span>
            
            <br>

            <!-- 运行天数提醒. -->
            
                <span id="sitetime"> Loading ...</span>
                <script>
                    var calcSiteTime = function () {
                        var seconds = 1000;
                        var minutes = seconds * 60;
                        var hours = minutes * 60;
                        var days = hours * 24;
                        var years = days * 365;
                        var today = new Date();
                        var startYear = "2019";
                        var startMonth = "6";
                        var startDate = "28";
                        var startHour = "0";
                        var startMinute = "0";
                        var startSecond = "0";
                        var todayYear = today.getFullYear();
                        var todayMonth = today.getMonth() + 1;
                        var todayDate = today.getDate();
                        var todayHour = today.getHours();
                        var todayMinute = today.getMinutes();
                        var todaySecond = today.getSeconds();
                        var t1 = Date.UTC(startYear, startMonth, startDate, startHour, startMinute, startSecond);
                        var t2 = Date.UTC(todayYear, todayMonth, todayDate, todayHour, todayMinute, todaySecond);
                        var diff = t2 - t1;
                        var diffYears = Math.floor(diff / years);
                        var diffDays = Math.floor((diff / days) - diffYears * 365);

                        // 区分是否有年份.
                        var language = 'zh-CN';
                        if (startYear === String(todayYear)) {
                            document.getElementById("year").innerHTML = todayYear;
                            var daysTip = 'This site has been running for ' + diffDays + ' days';
                            if (language === 'zh-CN') {
                                daysTip = '本站已运行 ' + diffDays + ' 天';
                            } else if (language === 'zh-HK') {
                                daysTip = '本站已運行 ' + diffDays + ' 天';
                            }
                            document.getElementById("sitetime").innerHTML = daysTip;
                        } else {
                            document.getElementById("year").innerHTML = startYear + " - " + todayYear;
                            var yearsAndDaysTip = 'This site has been running for ' + diffYears + ' years and '
                                + diffDays + ' days';
                            if (language === 'zh-CN') {
                                yearsAndDaysTip = '本站已运行 ' + diffYears + ' 年 ' + diffDays + ' 天';
                            } else if (language === 'zh-HK') {
                                yearsAndDaysTip = '本站已運行 ' + diffYears + ' 年 ' + diffDays + ' 天';
                            }
                            document.getElementById("sitetime").innerHTML = yearsAndDaysTip;
                        }
                    }

                    calcSiteTime();
                </script>
            
            <br>
            
        </div>
        <div class="col s12 m4 l4 social-link social-statis">
    <a href="https://github.com/kuangtianyu" class="tooltipped" target="_blank" data-tooltip="访问我的GitHub" data-position="top" data-delay="50">
        <i class="fab fa-github"></i>
    </a>



    <a href="mailto:1575235124@qq.com" class="tooltipped" target="_blank" data-tooltip="邮件联系我" data-position="top" data-delay="50">
        <i class="fas fa-envelope-open"></i>
    </a>







    <a href="tencent://AddContact/?fromId=50&fromSubId=1&subcmd=all&uin=1575235124" class="tooltipped" target="_blank" data-tooltip="QQ联系我: 1575235124" data-position="top" data-delay="50">
        <i class="fab fa-qq"></i>
    </a>





    <a href="https://www.zhihu.com/people/kuang-tian-yu-59" class="tooltipped" target="_blank" data-tooltip="关注我的知乎: https://www.zhihu.com/people/kuang-tian-yu-59" data-position="top" data-delay="50">
        <i class="fab fa-zhihu1">知</i>
    </a>



    <a href="/atom.xml" class="tooltipped" target="_blank" data-tooltip="RSS 订阅" data-position="top" data-delay="50">
        <i class="fas fa-rss"></i>
    </a>

</div>
    </div>
</footer>

<div class="progress-bar"></div>


    <!-- 搜索遮罩框 -->
<div id="searchModal" class="modal">
    <div class="modal-content">
        <div class="search-header">
            <span class="title"><i class="fas fa-search"></i>&nbsp;&nbsp;搜索</span>
            <input type="search" id="searchInput" name="s" placeholder="请输入搜索的关键字"
                   class="search-input">
        </div>
        <div id="searchResult"></div>
    </div>
</div>

<script type="text/javascript">
$(function () {
    var searchFunc = function (path, search_id, content_id) {
        'use strict';
        $.ajax({
            url: path,
            dataType: "xml",
            success: function (xmlResponse) {
                // get the contents from search data
                var datas = $("entry", xmlResponse).map(function () {
                    return {
                        title: $("title", this).text(),
                        content: $("content", this).text(),
                        url: $("url", this).text()
                    };
                }).get();
                var $input = document.getElementById(search_id);
                var $resultContent = document.getElementById(content_id);
                $input.addEventListener('input', function () {
                    var str = '<ul class=\"search-result-list\">';
                    var keywords = this.value.trim().toLowerCase().split(/[\s\-]+/);
                    $resultContent.innerHTML = "";
                    if (this.value.trim().length <= 0) {
                        return;
                    }
                    // perform local searching
                    datas.forEach(function (data) {
                        var isMatch = true;
                        var data_title = data.title.trim().toLowerCase();
                        var data_content = data.content.trim().replace(/<[^>]+>/g, "").toLowerCase();
                        var data_url = data.url;
                        data_url = data_url.indexOf('/') === 0 ? data.url : '/' + data_url;
                        var index_title = -1;
                        var index_content = -1;
                        var first_occur = -1;
                        // only match artiles with not empty titles and contents
                        if (data_title !== '' && data_content !== '') {
                            keywords.forEach(function (keyword, i) {
                                index_title = data_title.indexOf(keyword);
                                index_content = data_content.indexOf(keyword);
                                if (index_title < 0 && index_content < 0) {
                                    isMatch = false;
                                } else {
                                    if (index_content < 0) {
                                        index_content = 0;
                                    }
                                    if (i === 0) {
                                        first_occur = index_content;
                                    }
                                }
                            });
                        }
                        // show search results
                        if (isMatch) {
                            str += "<li><a href='" + data_url + "' class='search-result-title'>" + data_title + "</a>";
                            var content = data.content.trim().replace(/<[^>]+>/g, "");
                            if (first_occur >= 0) {
                                // cut out 100 characters
                                var start = first_occur - 20;
                                var end = first_occur + 80;
                                if (start < 0) {
                                    start = 0;
                                }
                                if (start === 0) {
                                    end = 100;
                                }
                                if (end > content.length) {
                                    end = content.length;
                                }
                                var match_content = content.substr(start, end);
                                // highlight all keywords
                                keywords.forEach(function (keyword) {
                                    var regS = new RegExp(keyword, "gi");
                                    match_content = match_content.replace(regS, "<em class=\"search-keyword\">" + keyword + "</em>");
                                });

                                str += "<p class=\"search-result\">" + match_content + "...</p>"
                            }
                            str += "</li>";
                        }
                    });
                    str += "</ul>";
                    $resultContent.innerHTML = str;
                });
            }
        });
    };

    searchFunc('/search.xml', 'searchInput', 'searchResult');
});
</script>

    <!-- 回到顶部按钮 -->
<div id="backTop" class="top-scroll">
    <a class="btn-floating btn-large waves-effect waves-light" href="#!">
        <i class="fas fa-arrow-up"></i>
    </a>
</div>


    <script src="/libs/materialize/materialize.min.js"></script>
    <script src="/libs/masonry/masonry.pkgd.min.js"></script>
    <script src="/libs/aos/aos.js"></script>
    <script src="/libs/scrollprogress/scrollProgress.min.js"></script>
    <script src="/libs/lightGallery/js/lightgallery-all.min.js"></script>
    <script src="/js/matery.js"></script>

    <!-- Baidu Analytics -->

    <!-- Baidu Push -->

<script>
    (function () {
        var bp = document.createElement('script');
        var curProtocol = window.location.protocol.split(':')[0];
        if (curProtocol === 'https') {
            bp.src = 'https://zz.bdstatic.com/linksubmit/push.js';
        } else {
            bp.src = 'http://push.zhanzhang.baidu.com/push.js';
        }
        var s = document.getElementsByTagName("script")[0];
        s.parentNode.insertBefore(bp, s);
    })();
</script>

    
    <script src="/libs/others/clicklove.js" async="async"></script>
    
    
    <script async src="/libs/others/busuanzi.pure.mini.js"></script>
    

    

    

    <!--腾讯兔小巢-->
    
    
    <script type="text/javascript" color="0,0,255"
        pointColor="0,0,255" opacity='0.7'
        zIndex="-1" count="99"
        src="/libs/background/canvas-nest.js"></script>
    

    
    
    <script type="text/javascript" size="150" alpha='0.6'
        zIndex="-1" src="/libs/background/ribbon-refresh.min.js" async="async"></script>
    

    
    <script type="text/javascript" src="/libs/background/ribbon-dynamic.js" async="async"></script>
    

    
    <script src="/libs/instantpage/instantpage.js" type="module"></script>
    

</body>

</html>
